Modeling the effect of tool edge radius on contact zone in nanomachining

The contact between tool and workpiece during nanomachining is a complicated phenomenon due to comparable tool edge radius, R, with cutting depth, a. This paper presents an investigation into the effects of tool edge radius on contact zone, chip formation mechanism, stagnation zone, tool forces and hydrostatic stress distributions. Molecular dynamics simulations of the nanometric cutting on single crystal copper were performed using EAM potential function with wide range from a/R = ∞ to tools with various rounded tip. Results showed that although at a/R ⩾ 1, both tool tip and rake edge participate in chip formation, at a/R < 1 chip is formed only by rounded edge. Also, at a/R < 1, a small fraction of atoms compared with a sharper tool are separated as chip and larger fraction is pressurized to pass beneath the tool edge. Indeed, in rounded edge tools, the stable stagnation zone is located in tool curvature tip that acts as the first effective cutting edge. The height of stagnation point from the bottom edge of tool increases with edge radius, where it is independent from undeformed chip thickness. In addition, cutting force is slightly increased at smaller a/R; however, the trust force is raised remarkably especially when cutting depth approaches to critical depth of cut. Smaller a/R, similarly, induced higher compressive hydrostatic stress in wider contact length. Finally, if cutting depth is lower than the height of stagnation zone, the cutting mechanism will change to sliding mechanism.